LTC1046

4

AMBIENT TEMPERATURE (

°C)

–55

26

30

32

34

36

38

40

25

50

100

125

1046 G11

28

–25

0

75

AMBIENT TEMPERATURE (

°C)

0

1

10

100

14

5

7

1046 G10

23

6

CC

HARA TERISTICS

A

TYPICALPERFOR

CE

TEST CIRCUIT

Figure 1

S

APPLICATI

I FOR ATIO

Theory of Operation

To understand the theory of operation of the LTC1046, a

review of a basic switched capacitor building block is

helpful.

In Figure 2, when the switch is in the left position, capacitor

C1 will charge to voltage V1. The total charge on C1 will be

q1 = C1V1. The switch then moves to the right, discharg-

ing C1 to voltage V2. After this discharge time, the charge

on C1 is q2 = C1V2. Note that charge has been transferred

from the source, V1, to the output, V2. The amount of

charge transferred is:

∆q = q1 – q2 = C1(V1 – V2).

If the switch is cycled “f” times per second, the charge

transfer per unit time (i.e., current) is:

I = f •

∆q = f • C1(V1 – V2).

Figure 2. Switched Capacitor Building Block

Oscillator Frequency as a

Oscillator Frequency vs

Function of Supply Voltage

Temperature

(Using Test Circuit in Figure 1)

EXTERNAL

OSCILLATOR

C2

10

µF

1046 F01

1

2

3

4

8

7

6

5

OSC

LV

BOOST

GND

LTC1046

C1

10

µF

+

C1

f

C2

1046 F02

V2

V1